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Questions and Answers
What is the term used to describe heart failure when compensatory mechanisms fail to maintain cardiac output?
Which class of drugs enhances cardiac contractility by increasing cytoplasmic calcium concentration?
What is the primary mechanism of action of digitalis glycosides like digoxin in increasing force of cardiac muscle contraction?
What is the most widely used digitalis glycoside that has a low therapeutic index?
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Which drug class is primarily responsible for inhibiting the renin–angiotensin–aldosterone system?
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What is the term used to refer to HF when a patient develops worsening signs and symptoms due to failure of compensatory mechanisms?
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What are the initial indicators of digoxin toxicity?
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What is a management strategy for severe digoxin toxicity that induces ventricular tachycardia?
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How should hypokalemia be managed in a patient predisposed to digoxin toxicity?
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What is the mechanism of action of digoxin immune Fab in the management of severe digoxin toxicity?
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Which drug class should be used with caution alongside digoxin due to their effect on AV conduction?
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What is the mechanism of action of β-agonists like dobutamine and dopamine?
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What is the mechanism by which increased cellular Na+ affects intracellular Ca2+ levels?
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What effect does digoxin toxicity have on the resting membrane potential of cardiac cells?
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How does digoxin toxicity affect the risk of arrhythmias in cardiac cells?
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What is a targeted serum drug concentration of digoxin in patients with HFrEF?
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What effect does digoxin have on heart rate and myocardial oxygen demand?
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Why is a low serum concentration of digoxin targeted in HFrEF patients?
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Study Notes
Heart Failure
- Decompensated heart failure occurs when compensatory mechanisms fail to maintain cardiac output.
Positive Inotropes
- Positive inotropes, a class of drugs, enhance cardiac contractility by increasing cytoplasmic calcium concentration.
Digitalis Glycosides
- Digitalis glycosides, such as digoxin, increase the force of cardiac muscle contraction by inhibiting the sodium-potassium ATPase, leading to an increase in cytoplasmic calcium concentration.
- Digoxin is the most widely used digitalis glycoside and has a low therapeutic index.
Renin-Angiotensin-Aldosterone System
- ACE inhibitors and ARBs are primarily responsible for inhibiting the renin-angiotensin-aldosterone system.
Decompensated Heart Failure
- Decompensated heart failure occurs when a patient develops worsening signs and symptoms due to failure of compensatory mechanisms.
Digoxin Toxicity
- Initial indicators of digoxin toxicity include nausea, vomiting, and visual disturbances.
- A management strategy for severe digoxin toxicity that induces ventricular tachycardia is administration of digoxin immune Fab.
- Hypokalemia should be managed by potassium replacement in a patient predisposed to digoxin toxicity.
- Digoxin immune Fab works by binding to digoxin, making it inactive.
Interactions with Digoxin
- β-blockers should be used with caution alongside digoxin due to their effect on AV conduction.
β-Agonists
- β-agonists like dobutamine and dopamine increase the force of cardiac contraction by increasing cytoplasmic calcium concentration.
Na+ and Ca2+ Levels
- Increased cellular Na+ affects intracellular Ca2+ levels by reducing the gradient for Ca2+ entry into the cell.
Effects of Digoxin Toxicity
- Digoxin toxicity causes an increase in the resting membrane potential of cardiac cells, making them more prone to arrhythmias.
Therapeutic Range of Digoxin
- A targeted serum concentration of digoxin in patients with HFrEF is 0.5-1.2 ng/mL.
- Digoxin reduces heart rate and myocardial oxygen demand, which is beneficial in HFrEF patients.
- A low serum concentration of digoxin is targeted in HFrEF patients to minimize the risk of toxicity.
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Description
Test your knowledge on the pharmacologic therapy used for heart failure, including inhibitors of the renin-angiotensin-aldosterone system, inhibitors of the sympathetic nervous system, diuretics, and inotropic agents.
